DC—DC converters usually contain an excess-current (short-circuit) protection circuit that limits the input or output current to a specified maximum value. A fast comparator is required in the excess-current protection circuit to detect the voltage drop across a sense resistor. The function of the comparator itself is dependent on a sufficient supply voltage. Conventionally, if the supply voltage drops below a normal operating level, the comparator is not operative any more, and the converter must be switched off to prevent excessive output current from damaging an appliance connected to the output of the converter even though the supply voltage, typically from a supply source such as a battery, is low.